Date   : Thu, 31 Jul 2003 01:00:50 +0100
From   : tom@...
Subject: BBC double density disc images

Hi,

I'm aware of the following disc formats, sides by tracks by sectors 
per track:

.SSD                   1x80x10
.DSD                   2x80x10
.ADL                   1x80x16 ADFS format
.ADM                   2x80x16 ADFS format

(It seems ADL/ADM must be ADFS format, because BeebEm checks certain 
bytes in the disc image.)

Does anyone have any suggestions (or existing standards) for 
extensions for 16-sector double density non-ADFS (like Watford DDFS, 
I believe), or 18-sector like Challenger/DDOS?

Alternatively, if there's no such thing as truncated double-density 
images I'll just use .SDD/.DDD and work out 16/18 sector based on the 
file size.

My gut inclination is indeed to disallow truncated DD images, because 
AnaDisk doesn't produce them and it's easy enough to read DD discs on 
a PC. So, SDD would always be 320K/360K and DDD would always be 
640K/720K. 

Thoughts?

--Tom